The data on place of work were derived from answers to Question 29, which was asked of people who indicated in Question 28 that they worked at some time during the reference week. (See "Reference Week.")
Data were tabulated for workers 16 years old and over, that is, members of the Armed Forces and civilians who were at work during the reference week. Data on place of work refer to the geographic location at which workers carried out their occupational activities during the reference week. In the American Community Survey, the exact address (number and street name) of the place of work was asked, as well as the place (city, town, or post office); whether the place of work was inside or outside the limits of that city or town; and the county, state or foreign country, and ZIP Code. In the Puerto Rico Community Survey, the question asked for the exact address, including the development or condominium name, as well as the place; whether or not the place of work was inside or outside the limits of that city or town; the municipio or U.S. county. Respondents also were asked to "enter Puerto Rico or name of U.S. state or foreign country" and the ZIP Code. If the respondent's employer operated in more than one location, the exact address of the location or branch where he or she worked was requested. When the number and street name were unknown, a description of the location, such as the building name or nearest street or intersection, was to be entered. People who worked at more than one location during the reference week were asked to report the location at which they worked the greatest number of hours. People who regularly worked in several locations each day during the reference week were requested to give the address at which they began work each day. For cases in which daily work did not begin at a central place each day, the respondent was asked to provide as much information as possible to describe the area in which he or she worked most during the reference week.

Place-of-work data may show a few workers who made unlikely daily work trips (e.g., workers who lived in New York and worked in California). This result is attributable to people who worked during the reference week at a location that was different from their usual place of work, such as people away from home on business.

In areas where the workplace address was geographically coded to the block level, people were tabulated as working inside or outside a specific place based on the location of that address regardless of the response to Question 29c concerning city/town limits. In areas where it was impossible to code the workplace address to the block level, or the coding system was unable to match the employer name and street address responses, people were tabulated as working inside or outside a specific place based on the combination of state, county, ZIP Code, place name, and city limits indicator. The city limits indicator was used only in coding decisions when there were multiple geographic codes to select from, after matching on the state, county, place, and ZIP Code responses. The accuracy of place-of-work data for census designated places (CDPs) may be affected by the extent to which their census names were familiar to respondents, and by coding problems caused by similarities between the CDP name and the names of other geographic jurisdictions in the same vicinity.

Place-of-work data are given for selected minor civil divisions (MCDs), (generally cities, towns, and townships) in the 12 strong MCD states (Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin), based on the responses to the place of work question. Many towns and townships are regarded locally as equivalent to a place, and therefore, were reported as the place of work. When a respondent reported a locality or incorporated place that formed a part of a township or town, the coding and tabulating procedure was designed to include the response in the total for the township or town.

Beginning in 2006, the group quarters (GQ) population is included in the ACS. Some types of GQ populations have place of work distributions that are different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the place of work distribution. This is particularly true for areas with a substantial GQ population.

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.

This term appears in connection with several subjects: employment status, journey-to-work questions, class of worker, weeks worked in the past 12 months, and number of workers in family in the past 12 months. Its meaning varies and, therefore, should be determined in each case by referring to the definition of the subject in which it appears. When used in the concepts "workers in family" and "full-time, year-round workers," the term "worker" relates to the meaning of work defined for the "work experience" subject.

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.

The data on age were derived from answers to Question 4. The age classification is based on the age of the person in complete years at the time of interview. Both age and date of birth are used in combination to calculate the most accurate age at the time of the interview. Inconsistently reported and missing values are assigned or imputed based on the values of other variables for that person, from other people in the household, or from people in other households ("hot deck" imputation). Data on age are used to determine the applicability of other questions for a particular individual and to classify other characteristics in tabulations. Age data are needed to interpret most social and economic characteristics used to plan and analyze programs and policies. Therefore, age data are tabulated by many different age groupings, such as 5-year age groups.

The median age is the age that divides the population into two equal-size groups. Half of the population is older than the median age and half is younger. Median age is based on a standard distribution of the population by single years of age and is shown to the nearest tenth of a year. (See the sections on "Standard Distributions" and "Medians" under "Derived Measures.")

Caution should be taken when comparing population in age groups across time. The entire population continually ages into older age groups over time and babies fill in the youngest age group. Therefore, the population of a certain age is made up of a completely different group of people in 2000 and 2008. Since populations occasionally experience booms/increases and busts/decreases in births, deaths, or migration (for example, the postwar Baby Boom from 1946-1964), one should not necessarily expect that the population in an age group in Census 2000 should be similar in size or proportion to the population in the same age group in the 2008 ACS. For example, Baby Boomers were age 36 to 54 in Census 2000 while they were age 44 to 62 in the 2008 ACS. Therefore, the age group 55 to 59 would show a considerable increase in population when comparing Census 2000 data with the 2008 ACS data. Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have age distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the age distribution. This is particularly true for areas with a substantial GQ population.

The 1996-2002 American Community Survey question asked for month, day, and year of birth before age. Since 2003, the American Community Survey question asked for age, followed by month, day, and year of birth. In 2008, an additional instruction was provided with the age and date of birth question on the American Community Survey questionnaire to report babies as age 0 when the child was less than 1 year old. The addition of this instruction occurred after 2005 National Census Test results indicated increased accuracy of age reporting for babies less than one year old.

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.

There are both legal and statistical American Indian, Alaska Native, and native Hawaiian entities for which the U.S. Census Bureau provides data for Census 2000. The legal entities consist of federally recognized American Indian reservations and off-reservation trust land areas, the tribal subdivisions that can divide these entities, state recognized American Indian reservations, Alaska Native Regional Corporations, and Hawaiian home lands. The statistical entities are Alaska Native village statistical areas, Oklahoma tribal statistical areas, tribal designated statistical areas, and state designated American Indian statistical areas. Tribal subdivisions can exist within the statistical Oklahoma tribal statistical areas.

In all cases, these areas are mutually exclusive in that no American Indian, Alaska Native, or Hawaiian home land can overlap another tribal entity, except for tribal subdivisions, which subdivide some American Indian entities, and Alaska Native village statistical areas, which exist within Alaska Native Regional Corporations. In some cases where more than one tribe claims jurisdiction over an area, the U.S. Census Bureau creates a joint use area as a separate entity to define this area of dual claims. The following provides more detail about each of the various American Indian areas, Alaska Native areas, and Hawaiian home lands.

Alaska Native Regional Corporations (ANRCs) are corporate entities established to conduct both business and nonprofit affairs of Alaska Natives pursuant to the Alaska Native Claims Settlement Act of 1972 (Public Law 92-203). Twelve ANRCs are geographic entities that cover most of the state of Alaska (the Annette Island Reserve-an American Indian reservation-is excluded from any ANRC). (A thirteenth ANRC represents Alaska Natives who do not live in Alaska and do not identify with any of the 12 corporations; the U.S. Census Bureau does not provide data for this ANRC because it has no geographic extent.) The boundaries of ANRCs have been legally established. The U.S. Census Bureau offers representatives of the 12 nonprofit ANRCs the opportunity to review and update the ANRC boundaries. The U.S. Census Bureau first provided data for ANRCs for the 1990 census.

Each ANRC is assigned a five-digit Federal Information Processing Standards (FIPS) code, which is assigned in alphabetical order by ANRC name.

Alaska Native village statistical areas (ANVSAs) are statistical entities that represent the densely settled portion of Alaska Native villages (ANVs), which constitute associations, bands, clans, communities, groups, tribes or villages, recognized pursuant to the Alaska Native Claims Settlement Act of 1972 (Public Law 92-203). ANVSAs are reviewed and delineated by officials of the ANV (or officials of the Alaska Native Regional Corporation (ANRC) in which the ANV is located if no ANV official chooses to participate in the delineation process) solely for data presentation purposes. An ANVSA may not overlap the boundary of another ANVSA, an American Indian reservation, or a tribal designated statistical area. The U.S. Census Bureau first provided data for ANVSAs for the 1990 census.

Each ANVSA is assigned a national four-digit census code ranging from 6000 through 7999. Each ANVSA also is assigned a state-based five-digit Federal Information Processing Standards (FIPS) code. Both the census and FIPS codes are assigned in alphabetical order by ANVSA name.

Federal American Indian reservations are areas that have been set aside by the United States for the use of tribes, the exterior boundaries of which are more particularly defined in the final tribal treaties, agreements, executive orders, federal statutes, secretarial orders, or judicial determinations. The U.S. Census Bureau recognizes federal reservations as territory over which American Indian tribes have primary governmental authority. These entities are known as colonies, communities, pueblos, rancherias, ranches, reservations, reserves, villages, Indian communities, and Indian villages. The Bureau of Indian Affairs maintains a list of federally recognized tribal governments. The U.S. Census Bureau contacts representatives of American Indian tribal governments to identify the boundaries for federal reservations.

Some state governments have established reservations for tribes recognized by the state. A governor-appointed state liaison provides the names and boundaries for state recognized American Indian reservations to the U.S. Census Bureau. The names of these reservations are followed by "(State)" in census data presentations.
Federal reservations may cross state boundaries, and federal and state reservations may cross county, county subdivision, and place boundaries. For reservations that cross state boundaries, only the portions of the reservations in a given state are shown in the data products for that state. Lands that are administered jointly and/or are claimed by two tribes, whether federally or state recognized, are called "joint use areas," and are treated as if they are separate American Indian reservations for data presentation purposes. The entire reservations are shown in data products for the United States. The U.S. Census Bureau first provided data for American Indian reservations in the 1970 census.
Each federal American Indian reservation is assigned a four-digit census code ranging from 0001 through 4999. These census codes are assigned in alphabetical order of American Indian reservation names nationwide, except that joint use areas appear at the end of the code range. Each state American Indian reservation is assigned a four-digit census code ranging from 9000 through 9499. Each American Indian reservation also is assigned a five-digit Federal Information Processing Standards (FIPS) code; because FIPS codes are assigned in alphabetical sequence within each state, the FIPS code is different in each state for reservations that include territory in more than one state.

Trust lands are areas for which the United States holds title in trust for the benefit of a tribe (tribal trust land) or for an individual Indian (individual trust land). Trust lands can be alienated or encumbered only by the owner with the approval of the Secretary of the Interior or his/her authorized representative. Trust lands may be located on or off of a reservation. The U.S. Census Bureau recognizes and tabulates data for reservations and off-reservation trust lands because American Indian tribes have primary governmental authority over these lands. Primary tribal governmental authority generally is not attached to tribal lands located off the reservation until the lands are placed in trust.

In the U.S. Census Bureau's data tabulations, off-reservation trust lands always are associated with a specific federally recognized reservation and/or tribal government. Such trust lands may be located in more than one state. Only the portions of off-reservation trust lands in a given state are shown in the data products for that state; all off-reservation trust lands associated with a reservation or tribe are shown in data products for the United States. The U.S. Census Bureau first provided trust land data for off-reservation tribal trust lands in the 1980 census; in 1990, the trust land data included both tribal and individual trust lands. The U.S. Census Bureau does not identify restricted fee land or land in fee simple status as a specific geographic category.

In decennial census data tabulations, off-reservation trust lands are assigned a four-digit census code and a five-digit Federal Information Processing Standards (FIPS) code that is the same as that for the reservation with which they are associated. As with reservations, FIPS codes for offreservation trust lands are unique within state, so they will differ if they extend into more than one state. The FIPS codes for such off-reservation trust lands are the same as those for the associated reservation. In the TIGER/Line® products, a letter code-" T" for tribal and "I" for individual- identifies off-reservation trust lands. In decennial census data tabulations, a trust land flag uniquely identifies off-reservation trust lands. Printed reports show separate tabulations for all off-reservation trust land areas, but do not provide separate tabulations for the tribal versus individual trust lands. Trust lands associated with tribes that do not have a reservation are presented and coded by tribal name, interspersed alphabetically among the reservation names.

American Indian tribal subdivisions are administrative subdivisions of federally recognized American Indian reservations, off-reservation trust lands, or Oklahoma tribal statistical areas (OTSAs), known as areas, chapters, communities, or districts. These entities are internal units of self-government or administration that serve social, cultural, and/or economic purposes for the American Indians on the reservations, off-reservation trust lands, or OTSAs.

The U.S. Census Bureau obtains the boundary and name information for tribal subdivisions from tribal governments. The U.S. Census Bureau first provided data for American Indian tribal subdivisions in the 1980 census when it identified them as "American Indian subreservation areas." It did not provide data for these entities in conjunction with the 1990 census.

Each American Indian tribal subdivision is assigned a three-digit census code that is alphabetically in order and unique within each reservation, associated off-reservation trust land, and OTSA. Each tribal subdivision also is assigned a five-digit Federal Information Processing Standards (FIPS) code. FIPS codes are assigned alphabetically within state; the FIPS codes are different in each state for tribal subdivisions that extend into more than one state.

Hawaiian home lands (HHLs) are areas held in trust for native Hawaiians by the state of Hawaii, pursuant to the Hawaiian Homes Commission Act of 1920, as amended. The U.S. Census Bureau obtained the names and boundaries of HHLs from state officials. HHLs are a new geographic entity for Census 2000.
Each HHL area is assigned a national four-digit census code ranging from 5000 through 5499 based on the alphabetical sequence of each HHL name. Each HHL also is assigned a five-digit Federal Information Processing Standards (FIPS) code in alphabetical order within the state of Hawaii.

Oklahoma tribal statistical areas (OTSAs) are statistical entities identified and delineated by the U.S. Census Bureau in consultation with federally recognized American Indian tribes in Oklahoma that do not currently have a reservation, but once had a reservation in that state. Boundaries of OTSAs will be those of the former reservations in Oklahoma, except where modified by agreements with neighboring tribes for data presentation purposes. OTSAs replace the "tribal jurisdiction statistical areas" of the 1990 census. The U.S. Census Bureau first provided data for the former Oklahoma reservations in conjunction with the 1980 census, when it defined a single allencompassing geographic entity called the "Historic Areas of Oklahoma (excluding urbanized areas)."

Each OTSA is assigned a national four-digit census code ranging from 5500 through 5999 based on the alphabetical sequence of each OTSAs name, except that the joint use areas appear at the end of the code range. Each OTSA also is assigned a five-digit Federal Information Processing Standards (FIPS) code in alphabetical order in Oklahoma.Opar

State designated American Indian statistical areas (SDAISAs) are statistical entities for state recognized American Indian tribes that do not have a state recognized land base (reservation). SDAISAs are identified and delineated for the U.S. Census Bureau by a state liaison identified by the governor's office in each state. SDAISAs generally encompass a compact and contiguous area that contains a concentration of people who identify with a state recognized American Indian tribe and in which there is structured or organized tribal activity. A SDAISA may not be located in more than one state unless the tribe is recognized by both states, and it may not include area within an American Indian reservation, off-reservation trust land, Alaska Native village statistical area, tribal designated statistical area (TDSA), or Oklahoma tribal statistical area. The U.S. Census Bureau established SDAISAs as a new geographic statistical entity for Census 2000, to differentiate between state recognized tribes without a land base and federally recognized tribes without a land base. For the 1990 census, all such tribal entities had been identified as TDSAs.

Each SDAISA is assigned a four-digit census code ranging from 9500 through 9999 in alphabetical sequence of SDAISA names nationwide. Each SDAISA also is assigned a five-digit Federal Information Processing Standards (FIPS) code in alphabetical order within state.

Tribal designated statistical areas (TDSAs) are statistical entities identified and delineated for the U.S. Census Bureau by federally recognized American Indian tribes that do not currently have a federally recognized land base (reservation or off-reservation trust land). A TDSA generally encompasses a compact and contiguous area that contains a concentration of people who identify with a federally recognized American Indian tribe and in which there is structured or organized tribal activity. A TDSA may be located in more than one state, and it may not include area within an American Indian reservation, off-reservation trust land, Alaska Native village statistical area, state designated American Indian statistical area (SDAISA), or Oklahoma tribal statistical area. The U.S. Census Bureau first reported data for TDSAs in conjunction with the 1990 census, when both federally and state recognized tribes could identify and delineate TDSAs. TDSAs now apply only to federally recognized tribes. State recognized tribes without a land base, including those that were TDSAs in 1990, are identified as SDAISAs, a new geographic entity for Census 2000.

Each TDSA is assigned a four-digit census code ranging from 8000 through 8999 in alphabetical sequence of TDSA names nationwide. Each TDSA also is assigned a five-digit Federal Information Processing Standards (FIPS) code in alphabetical order within state; because FIPS codes are assigned within each state, the FIPS code is different in each state for TDSAs that extend into more than one state.